This invention relates generally to the provision of cooling or refrigeration and, more particularly, to the provision of cooling or refrigeration to superconducting cable.
Superconductivity is the phenomenon wherein certain metals, alloys and compounds at very low temperatures lose electrical resistance so that they have infinite electrical conductivity.
It is important in the use of superconducting cable to transmit electricity, that the cooling, i.e. refrigeration, provided to the superconducting cable not undergo interruption lest the cable lose its ability to superconduct and the electrical transmission be compromised. While systems which can provide the requisite refrigeration to superconducting cable are known, such systems, such as closed loop turbo mechanical refrigeration systems, are costly, complicated and subject to breakdown, necessitating the use of back up systems to ensure uninterrupted cooling of the superconducting cable.
Accordingly, it is an object of this invention to provide a reliable method for providing cooling to superconducting cable which can be used as the primary or a back up means for providing cooling to superconducting cable.
The above and other objects, which will become apparent to those skilled in the art upon a reading of this disclosure, are attained by the present invention, one aspect of which is:
A method for providing cooling to superconducting cable comprising:
(A) passing liquid cryogen from a storage vessel to a vacuum vessel, and flashing a portion of the liquid cryogen into the vacuum vessel to produce vapor and cooled liquid cryogen within the vacuum vessel;
(B) pumping vapor out from the vacuum vessel; and
(C) passing cooled liquid cryogen from the vacuum vessel to superconducting cable and providing cooling from the cooled liquid cryogen to the superconducting cable.
Another aspect of the invention is:
A method for providing cooling to superconducting cable comprising:
(A) passing liquid cryogen from a storage vessel to a vacuum vessel, and flashing a portion of the liquid cryogen into the vacuum vessel to produce vapor and cooled liquid cryogen within the vacuum vessel;
(B) pumping vapor out from the vacuum vessel; and
(C) cooling refrigerant fluid by indirect heat exchange with the cooled liquid cryogen to produce cooled refrigerant fluid, passing the cooled refrigerant fluid to superconducting cable, and providing cooling from the cooled refrigerant fluid to the superconducting cable.
As used herein the term xe2x80x9ccryogenic temperaturexe2x80x9d means a temperature at or below 120K.
As used herein the term xe2x80x9csuperconducting cablexe2x80x9d means cable made of material that loses all of its resistance to the conduction of an electrical current once the material attains some cryogenic temperature.
As used herein the term xe2x80x9crefrigerationxe2x80x9d means the capability to reject heat from a subambient temperature entity.
As used herein the term xe2x80x9cindirect heat exchangexe2x80x9d means the bringing of entities into heat exchange relation without any physical contact or intermixing of the entities with each other.
As used herein the term xe2x80x9cdirect heat exchangexe2x80x9d means the transfer of refrigeration through contact of cooling and heating entities.
As used herein the term xe2x80x9cvacuum vesselxe2x80x9d means a vessel which has an internal pressure less than the pressure of liquid cryogen passed into the vacuum vessel from a storage vessel.
As used herein the term xe2x80x9cvacuum pumpxe2x80x9d means a compressor used to move gas from subatmospheric pressure to atmospheric pressure.
As used herein the term xe2x80x9cflashingxe2x80x9d means the vaporization of a portion of liquid wherein the portion of liquid vaporized absorbs latent heat of vaporization from its surroundings and therefore cools its surroundings. In this case, the remaining liquid not vaporized is cooled. Lowering the vapor pressure of the liquid induces flashing.